Per the documentation in the header, base::StringPiece should be passed
by value, not by const reference.
Bug:
Change-Id: I21351fcb901f5ef89fa7b84af0721d483b333810
Reviewed-on: https://chromium-review.googlesource.com/754584
Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514181}